Reverse stop for power tongs

ABSTRACT

A power tong for making up and breaking out pipe joints, in which pipe gripping jaws are actuated to pipe gripping positions from retracted positions responsive to relative rotation in either direction between a jaw carrying member and an actuator member, and the jaws are retracted upon reverse relative rotation in the opposite direction, and reverse stop means are provided to prevent reverse relative rotation of said members past the positions at which the jaws are retracted. The reverse stop means includes alternately positionable stops carried by one of the members engageable with alternately spaced stops on the other member to limit reverse relative rotation.

Elnited States Patent Wilms 1 Dec. 19, 1972 [54] REVERSE STOP FOR POWER TONGS Primary Examiner.lames L. Jones, Jr. 72 Inventor: Carl Alfred Wilms, La Habra, Calif. Banner wmam mum) and John W. Butcher [73] Assignee: Byron Jackson, lnc., Long Beach,

Calif- [57] ABSTRACT Filed: April 16, 1971 A power tong for making up and breaking out pipe [21] APPL NO; 134,661 joints, in which pipe gripping jaws are actuated to pipe gripping positions from retracted positions responsive to relative rotation in either direction between a jaw [52] U.S.Cl ..8l/57.l8 carrying member and an actuator member, d the [51] 111t- CI. j are t t d upon reverse l ti t ti i th [58] Field of Search ..81/57.18, 57.21, 57.16 Opposite direction and reverse stop means are vided to prevent reverse relative rotation of said mem- [56] References C'ted bers past the positions at which the jaws are retracted. UNITED STATES PATENTS The reverse stop means includes alternately positionable stops carried by one of the members engageable 3,550,485 12/1970 Dickmann ..81/57.18 with alternately spaced stops on the other member to 3,548,692 12/1970 Dickmann ..8l/57.18 reverse relative rotation I 3,180,186 4/1965 Catland ..81/57.l8

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PATENTED um 19 m2 SHEET 6 BF 6 INVENTOR ('AFZ A. W/(Mfi 1 REVERSE sror ron rowan TONGS BACKGROUND OF THE INVENTION In the development of power tongs, for making up and breaking out threaded joints, such as drill pipe tool joints, tubing couplings, casing couplings, and the like, double acting tongs have evolved which are operative in either direction to grip and rotate a length of pipe, or the like, supported in a derrick, while a stationary length of pipe, or the like, is suspended in the well and held against rotation by a back up tong or by the rotary table. Such tongs are a great improvement over the prior tongs which operated in only one direction and therefore required either a change of gripping components for reverse operation or that the tong be rolled over.

Dual acting power tongs of the type here involved, in general, have means for actuating pipe gripping jaws into gripping engagement with the pipe from retracted positions, responsive to relative rotation between ajaw carrying member and a jaw actuating member,in either direction, and thereafter, when the jaws are in gripping engagement with the pipe, the members are rotated together to turn the pipe in either direction. When the jaws are to be released from the pipe and retracted, the jaw carrying member and jaw actuating member are reversely relatively rotated and the jaws retracted. Since the gripping means are dual acting, means are typically provided which are adapted to stop relative rotation of the members in the respective reverse directions when the jaws are fully retracted, so that continued reverse relative rotation is prevented and the jaws, thus, cannot be re-closed on the pipe.

Particularly in large, massive tongs with high torque capacity for making up and breaking out well drilling pipe tool joints or making up casing joints, the means for stopping reverse relative rotation of the jaw carrying and jaw actuating members must be rugged and capable of sustaining without damage high shock loads, say when the gripping means is reversed at high speed to open the jaws. In addition to the need for rugged, durable reverse stop means in such tongs, the reverse stop means should also be easily and reliably operable between alternate positions for stopping relative rotation of the jaw carrying and jaw actuating members when the jaws are fully retracted during operation of the tong in opposite directions during the making up or breaking out of the joints.

It is also a problem solved in the prior art by coengageable stops, separate from the reverse stop means to limit relative rotation of the jaw carrying and jaw actuating members in a jaw closing direction, so that in the absence of a pipe between the jaws, the i'elatively rotatable members cannot relatively rotate to such an extent that they become out of phase.

THE PRIOR ART The tong disclosed in Letters Pat. of the US. No. 3,548,692, granted Dec. 22, 1970, for Well Pipe Tongs, is exemplary of the prior art in respect of alternately positionable reverse stop means in power tongs of the type here involved.

SUMMARY OF THE INVENTION The present invention provides a rugged, durable, yet simple, reverse stop means for power pipe tongs having relatively rotatable jaw carrying and jaw actuating members, whereby the members are caused to rotate together following reverse relative rotation of the members to positions at which the jaws are fully retracted.

More particularly, the reverse stop means includes an alternately positionable stop member carried by one of said relatively rotatable members and cooperative stop elements carried by the other of said relatively rotatable members, whereby the alternately positionable stop member is movable from a first position cooperative with certain of said stop elements for limiting or stopping relative rotation of said relatively rotatable members in one direction, to a second position at which said alternately positionable stop member is cooperative with certain other stop elements for limiting or stopping relative rotation of said relatively rotatable members in the opposite direction. Means are provided for moving said alternately positionable member between its two positions.

In addition, the reverse stop means is so constructed that-the relatively rotatable members are limited in the extent of relative rotation in a jaw closing direction so that the cooperative means for actuating the jaws to the pipe gripping position cannot over-travel and become out of phase when the jaws are actuated towards pipe gripping positions in the absence of a pipe between the aws.

In accomplishing the foregoing, the present invention provides a traveling stop carried by one of the relatively rotatable jaw carrying and jaw actuating members and a cooperative stop on the other of said members, one of the stops having circumferentially spaced angularly extended lugs with one lug also spaced axially from the other lug at opposite sides of the space between the lugs, and the cooperative stop has a lug circumferentially extended and axiallyshiftable in the circumferential space between the spaced lugs so as to be alternately positionable for engagement with one or the other of said circumferentially spaced lugs, depending upon the direction of relative rotation of said relatively rotatable members. Means are also provided for shifting the cooperative stop axially to its alternate positions.

In its preferred form, the stop means are constructed so that the stop lugs of both stops are angularly extended a sufficient distance that a plurality of the cooperative lugs are provided in circumferentially spaced sets, say at diametrically opposite sides of the gripping assembly, so that the relatively rotatable members can move the full range necessary to close the jaws on a wide range of pipe sizes, but in the absence of a pipe between the jaws, the stop lugs also coengage to prevent reclosure of the jaws and mislocation of the jaw actuator means with respect to the jaws. In other words, the relatively rotatable members cannotget out of phase.

Stop means of the invention, due to the lug form and angular extent, are rugged and durable and, therefore, capable of sustaining without damage the high shock loads imposed thereon during opening of the jaws.

This invention possesses many other advantages, and has other purposes which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It.will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan of a power tong made in accordance with the invention, with portions of the housing broken away, to expose the interior structure, with the gripping jaws retracted;

FIG. 2 is a vertical section, as taken on the line 22 of FIG. 1;

FIG. 3 is a view corresponding to FIG. 1, but showing the gripping jaws in pipe gripping positions and the actuator means shifted to break out a joint of pipe;

FIG. 4 is an enlarged vertical section, as taken on the line 4-4 of FIG. 2, and showing a typical actuator slide construction;

FIG. 5 is a horizontal section, as taken on the line 5- 5 of FIG. 2, with parts broken away to show the reverse stop and brake means of the invention;

FIG. 6 is an enlarged fragmentary, vertical section, as taken on the line 6-6 of FIG. 5 showing the details of a brake unit;

FIG. Tis a fragmentary vertical section, as taken on the line 7-7 of FIG. 6, showing the reverse stop means in a make up condition;

FIG. 8 is a view generally corresponding to FIG. 7, but showing the reverse stop means actuated to the break out condition;

FIG. 9 is a vertical section, as taken on the line 9-9 of FIG. 7;

FIG. 10 is a vertical section, as taken on the line 10- 10 of FIG. 8; and

FIG. 11 is a schematic diagram of the control and operating system for the tong.

DESCRIPTION OF THE PREFERRED EMBODIMENT As seen in the drawings, the tong assembly comprises a body or housing l-I defining an openingO for a pipe and in which is rotatably supported pipe gripping means G, including a number of circumferentially spaced gripping jaws J, carried by an inner, jaw-carrying ring or rotatable member 10, and actuatable radially of the assembly from retracted positions, as seen in FIG. 1, to pipe gripping positions, as seen in FIG. 3, in response to rotation of an outer rotative member or cam ring 11, by drive means including one or more drive chains 12, a fluid pressure operated, rotary, chain driving, spinning motor M, and, depending on whether the tong is being used to make up or break out pipe joints, break out actuator cylinder means B0 and make up actuator cylinder means MU, each of which actuator cylinder means operatively engages a portion or run of the chain or chains 12 between the motor M and the outer ring 11, whereby extension of the respective cylinder means will apply a pull to the respective run of the chain and effect angular movement of the outer ring 11 in one direction or the other, while the motor M or its chain drive shaft is locked by lock means L.

More particularly, as best seen in FIG.2, the housing H comprises an annular body 20 to which is suitably affixed, as by fasteners 21, a top annular plate 22. Centrally of the plate 22 is a guide ring support 23, at-.

tached to the plate 22 by fasteners 24'and having a guide insert 23a defining the open top of the pipe opening 0. A bottom plate 25, affixed to the body 20 by fasteners 26, combines with the body 20 and the top plate 22 to form an annular space in which the inner ring 10 and outer ring 11 areconcentrically disposed for rotation.

The annular body 20 supports the outer ring 11 for rotative movement on suitable ball bearings 27 The inner ring 10 is a composite assembly, including an annular central section 28 which defines the pipe opening 0 and has radial windows 29 through which the jaws J are radially reciprocable between retracted and pipe gripping positions. Formed on or otherwise provided on the central section 28 of the inner ring 10 is an outwardly extended flange 280, at the outer periphery of which are suitable ball or other bearings 30 engaged with a retaining race member 31 attached to the outer ring 11, as by fasteners 32. Thus, it is seen that the outer'ring 11 is revolvable within the housing body 20 on the bearings 27 and the outer ring 11 is revolvable relative to the inner, jaw-carrying ring 10 for a purpose which will be later described.

The gripping jaws J are box-like and comprise a top wall 33, a bottom wall 34 and an inner end wall 35, the latter being adapted, as customary, to receive an assortment of die carriers 36 having pipe gripping dies 37 removably carried thereby. Further details of the die carriers are not germane to the present invention, and it will be understood that the use of die carriers of different dimensions radially of the pipe opening 0 enables effective use of the tong on pipe of a wide range'of diameters. In order to actuate the jaws J to pipe gripping positions, from retracted positions, each jaw has a cam roller 40 joumaled between the top and bottom walls 33, 34 on a pin 41, or other suitable support, and the outer ring 11 has a cam surface 42 which defines the inner periphery of the outer ring. Such a cam and roller, tong jaw-actuating means .is well known, as are other jaw-actuating means responsive to relative rotation of the inner and outer rings of tongs. As is well known in power tongs useful in making up and breaking out pipe joints, without requiring that the tong be rolled over top to bottom, the cam surface 42 is compound, as seen in FIG. 1, for example. This is to say that operable on the roller 40 of each jaw, the cam surface 42 includes a make up ramp 42M and a break out ramp 428 at opposite sides of central portions 43, these latter portions being indented to allow full retraction of the jaws J at the mid-point of the compound cams 42M and 428. The illustrated tong assembly has means for effecting positive retraction of the jaws J, as distinguished from spring loaded retraction, in the form of an outer cam surface 44 having portions which parallel the make up and break out ramps 42M and 42B and a cam follower pin 45 carried by each jaw and engaged with the cam surface 44.

hold the inner ring stationary, until the jaws J are locked up on a pipe or are being retracted from engagement with the pipe. In addition, reverse stop means are customarily provided to limit reverse relative rotation of the inner and outer rings 10 and 1-1 to a point at which the jaws are fully retracted and to prevent reclosure of the jaws on the pipe, as might otherwise be caused by continued relative rotation of the inner and outer rings, say,'so that the jaw rollers 40 would travel down the make up ramps 42M, during retraction of the jaws J following the making up ofa joint, and continue on past the central depressions 43 and up the break out ramps 42B of the cam surface 42. Brake means are herein shown at B, and reverse stop means are shown at RS, the details of both of which will be hereinafter more fully described.

In order to drive the outer ring 1 1, it is provided with sprocket means, including a pair of vertically spaced sprocket rings 50, 50 extending about the outer periphery of the outer ring 11 and afiized thereto for rotation therewith by a number of pins 51 and retaining fasteners 52. Each sprocket 50 is engaged by one of the drive chains 12, and these chains are driven by power operated means now to be described, and including the reversible fluid motor M and the make up actuator cylinder MU an the break out actuator cylinder BO.

Included in the tong body or housing H is a base section 66 for the power means, this base section being suitably secured to a rear portion 61 of the body member 20, as by fastenings 62. A cover plate 63 is provided for the base housing section 60 and is secured to the latter by fasteners 64. The fluid motor M is suitably mounted on the top plate 63, as by fasteners 65 which engage in a mounting flange 66 of the top plate.

To drive the chains 12, the fluid motor M has its output shaft 67 splined or otherwise drivingly connected to a sprocket drive shaft 68 which is joumaled in an upper bearing 69 and a lower bearing 70, these bearings being interposed between the sprocket shaft 68 and removable bearing caps 71 and 72 affixed to the housing by respective fasteners 73 and 74.

Fixed on the sprocket shaft 68 for rotation with the latter, as by keys 75, are a pair of drive sprockets 76, 76 which are engaged with the chains 12 to drive the latter in response to the rotation of the motor output shaft 67 in either direction. Disposed between the sprockets 76 on the sprocket shaft 68 and fixed on the shaft for rotation with the latter by the keys 75 is a sprocket shaft locking gear 77 forming part of the locking means L, previously referred to, s by which the chains 12 are anchored during final make up and initial break-out of a pipe joint. This locking gear has teeth 78 adapted for engagement by complemental teeth 79 on the confronting end of a locking dog 80. The dog 80 is reciprocable between a retracted position and a position at which its teeth 79 mesh with the teeth 78 of the locking gear 77, as generally seen in FIGS. 1 and 3, respectively. Ears 82, 82 formed in the base 60 and having tongue and groove connections at 83, 83 with the dog support the latter for reciprocation, and actuator means, in the illustrated form of a pressure operated actuator cylinder 84 having an extensible rod 85 are adapted to actuate the lock dog or slide 80 between its two positions. Suitable support and anchor means for the actuator cylinder 84 are shown as a yoke member 86 affixed to the ears 82 by fasteners 87 and to which one end of the cylinder 84 is pivotally connected at 88.

It is now apparent that the fluid motor M is capable of driving the chain drive oppositely, when the lock dog 80 is retracted, to-spin the gripping means G of the tong in either direction when spinning up and spinning out pipe joints. In addition, the motor drive, when locked.

by the dog 80, anchors the chains'12 so that the runs of the chains between the locked-sprockets 78 and the outer ring 11 may be actuated by the actuator cylinder means MU and BO toalso actuate the gripping means G through an arc of motion sufficient and at sufficient torque to finally make up or initially break out a pipe joint.

As seen in FIGS. 1, 3 and 4 to best advantage, the make up actuator cylinder means MU includes a pressure cylinder which has an ear 101 at one end pivotally connected or otherwise affixed by a pin 102 to the tong housing H; The cylinder 100 has a fluid connector 103 for the admission and exhaust of pressure fluid. A piston 104 within the cylinder 100 has a rod I 60 of the housing l-l.

Extending vertically through the block 106 is a sprocket shaft 113 having upper and lower idler sprockets 114 and 115, respectively, mounted for rotation on suitable bearings 116 and 117 which are retained in place, by keeper plates 119 and 120 affixed to the shaft ends by respective fasteners 121 and 122. The runs of the chains 12 between the spinning motor sprockets 78 and the outer ring sprockets 50 engage the idler sprockets 114 and 115, and, upon extension and retraction of the cylinder 100 and rod 105, are extended in loops along a plane parallel to the plane of the axes of the outer ring sprockets 50 and the motor sprockets 114 and to avail of the mechanical advantage, as well as to increase the total angular movement of the gripping means G for a given actuator stroke, with resultant savings in overall size of of the tong assembly.

The break out actuator cylinder means B0 are essentially the same as the make up actuator cylinder means i 135 or allow retraction of the rod, as the slide block 136 is moved along guide rails 140 carried on flanges 142 within the case base 60. This slide block 136 carriesa sprocket shaft on which sprockets like the sprockets 114 and 115 are rotatably supported, only the upper sprocket 114 being seen in FIGS. 1 and 3. Since the details of the idler sprocket and slide assembly of the break out actuator cylinder means correspond to those of the make up actuator cylinder means MU, no further specific description is believed to be necessary, except to note that the break out ac tuator cylinder means acts on the runs of chains 12 between the spinning motor sprocket 78 and the outer ring sprockets 50 to move the outer ring 11 in the opposite direction from the direction in which the outer ring 11 is moved by the make up cylinder means MU, when pressure fluid is supplied to either the make up cylinder 100 or the break out cylinder 130, alternately, as will be later described.

. The brake means B, previously referred to, for initially holding the inner jaw carrying ring or member against rotation with the outer ring, in order to set the jaws J in gripping engagement with the pipe, are best seen in'FIGS. 2, 5 and 6. I

More particularly, the brake means B comprises a brake disc or ring member 150 affixed at its inner periphery by fasteners 151 to a shoulder 152 on the inner ring and extending radially in a horizontal plane, and means for braking engagement with the opposing faces of the brake disc 150, in the form of a plurality of caliper type brake units 153 suitably spaced about and affixed by fasteners 154 to a radial flange 155 formed on the top plate 22 on the tong housing I-I.

Each brake unit 153, as best seen in FIG. 6, comprises a horizontally split body providing an upper cylinder section 156 having a piston chamber 157 opening towards the upper face of the brake disc 150 and a lower cylinder section 158 providing a piston chamber 159. Each of the piston chambers 157 and 159 contains a piston 160 provided with a suitable annular seal 161, whereby the pistons are adapted to be forced by fluid pressure admitted to the chambers 157 and 159 toward one another. Friction pads 162 are provided on the pistons 160 for frictional engagement with the disc 150. Fluid under pressure is admitted to the piston chambers 157 and 159 by means of a passage 163 which communicates with both chambers and with an inlet 164 to which fluid is supplied from a supply conduit 165. Since it is desired that the brake units 153 be simultaneously engaged with the disc 150 or effectively released, the conduit 165 is connected to each of the brake units, and a common source supplies pressure fluid to all chambers 157 and 159 of all units 153. For example, in FIG. 6, the housing flange 22 is ported at 166 and a supply conduit 167 communicates with the port 166 and with additional supply porting 168 in the housing H to conduit fluid from a source to the brake fluid conduit 165, under the control of means which control the braking action, as will be later described in respect of the control system of FIG. 11.

As previously indicated, the reverse stop means RS are provided to limit rotation of the outer or cam ring 11 relative to the inner or jaw carrying ring in a reverse direction to open the jaws J after a pipe joint is made up or broken out. To accomplish this, the reverse stop means permits the outer ring 1 1 to rotate relative to the inner ring 10 in a selected direction, clockwise for making up joints and counter clockwise for breaking out joints, so that cam surfaces 42M or 428, respectively,

may force the jaws J inwardly to pipe gripping posi- 10 in the reverse, jaw retracting direction, past the location at which the jaws arefully retracted, and the cam rollers 35 of the jaws J are in the depressions 43 of the cam surface 42.

The reverse latch means RS are best seen in FIGS. 2 and-5 through 10. More particularly, the reverse stop means includes a stop member 170 in the form of a ring concentrically mounted upon a support flange ,171 which is secured by fasteners 172 to theinner or jaw carrying ring 10 anda companion stop member in the form of a ring 174 on the outer ring 1 1, herein shown as an upward extension of the bearing ring 31 which'provides a race for the ball bearings 30 on which the inner and outer rings 10 and 11 relatively revolve.

In FIGS. 6-10, it will be seen that thestop ring 170 is vertically shiftable and has a splined connection 175 with the flange 171 on the jaw carrying ring 10. A suitable number of oiled compression springs 176 are interposed between the stop ring 170 and an opposing portion of thelnner ring 10 to provide means for biasing or moving the stop rings 170 to an upper, normal position, as seen in FIG. 6, 7 and 9, and actuator means 177 are provided for shifting the stop ring 170 downwardly to a position, as seen in FIGS. 8 and 10, the upper position being the make up stop position and the lower position being the break out stop position.

The actuator means 177 includes an angularly shiftable ring 178 disposed above the stop ring 170. Bearing means, such as balls 179, are interposed between the actuator ring 178 and the stop ring 170 to facilitate rotation of the latter relative to the former, since the stop ring 170 is carried by the revolvable gripping assembly G.

Double acting fluid pressure operated cylinder means, including a pair of cylinders 180,180, FIGS. 5 and 6, are connected with the actuator ring 178 at 181 and with the housing top flange 22 at 182, so as to effect angular movement of the actuator ring 178 in opposite directions relative to the housing.

Means are provided comprising a suitable number of fixed cams 183 formed on or affixed to the housing top plate 22 by fasteners 184, and a corresponding number of traveling cams 185, formed on or affixed to the actuator ring 178 by fasteners 186, whereby angular movement of the actuator ring 178 in the direction of the arrow in FIG. 8 will effect downward movement of the stop ring 170 from the upper position of FIGS. 7 and 9 to the lower position of FIGS. 8 and 10, as indicated by the arrow in FIG. 7. Obviously, movement of the actuator ring 178 from the position of FIGS. 8 and 10m that of FIGS. 7 and 9, allows the springs 176 to return the stop ring 170 to thenormal or upper position. Such actuation will be further described hereinafter in relation to the control system of FIG. 11.

The stop ring 170, on its outer periphery, has a pair of circumferentially extended stop lugs 170a, herein shown in FIG. as extending substantially 60 about the ring 170 and diametrically spaced. On the end of each lug 170a facing in a counter clockwise direction is a stop face or abutment 170m, which, as will later appear, stops rotation of the outer ring 11 relative to the inner ring when the tong is being used to make up joints and the jaws J are fully retracted. At the other end of each lug 170a facing in a clockwise direction, is a face or abutment 170b, which, as will later appear, stops rotation of the outer ring 11 relative to the inner ring 10 when the tong is being used to break out joints and the jaws J are fully retracted.

The reverse stop ring or member 174 cooperates with the stop lugs 170a to limit jaw-opening relative rotation of the inner ring 10 and the outer ring 11, and for this purpose, the ring 174 has upper stop lugs 174a and lower stop'lugs 174C extending circumferentially on the inner periphery. of the ring 174 and arranged so that these lugs are alternately located about the ring 174 at opposite sides of diametrically spaced vertical spaces or slots 174d having an angular extent substantially the same or slightly greater than the angular extent of the respective stop lugs 170a on the stop ring 170, whereby the lugs 170a may move vertically in the slots 174 between the upper and lower stop positions, previously referred to.

When the reverse stop actuator means is conditioned, as seen in FIG. 5, 6, 7 and 9, for making up joints with the tong, with the reverse stop ring 170 in the upper position, the upper stop lugs 1740 on the ring 174 provide, on their ends 174m facing in a clockwise direction, abutments cooperative with the ends 170m of the stop lugs 170a of the stop ring 170 to stop counter clockwise rotation of the outer ring 11 relative to the inner ring 10 at a location with the jaws retracted, but the lugs 170a will pass above the lower stop lugs 1740 (See FIG. 9), so that'the outer ring 11 is free to rotate in a clockwise direction relative to the inner ring 10 to close the jaws on and rotate a pipe. Alternatively, when the stop ring 170 is actuated to the lower position of FIGS. 8 and 10, for breaking out joints with the tong, the lower stop lugs 1740 on the ring 174 provide on their end 17% facing in a counter clockwise direction abutments cooperative with the ends 170b of the stop lugs 170a of the stop ring 170 to limit clockwise rotation of the outer ring 11 relative to the inner ring 10 at a location at which the jaws J are retracted, but the lugs 170a will pass beneath the upper stop lugs 174a (See FIG. 10), so that the outer ring 11 is free to rotate in a counter clockwise direction to close the jaws J and rotate a pipe.

In the illustrated tong, three jaws J are shown and the outer ring 11 may move through an arc of approximately 60 in either direction from a jaw retracted position to a position at which the jaws engage the pipe. Thus, the stop lugs 170a on the stop ring 170 and the stop lugs 174a and 174c on the stop ring 174 are angularly spaced to provide slots 174d of about 60 extent and Y themselves extend about 60, so that in the illustrated tong, a stop lug 174a, an adjacent slot 174d and a stop lug 1174c, each of about 60 in extent are located on each diametrically opposed half of the stop ring 174. Other arrangements are possible depending on the number of jaws and the angular motion necessary to actuate the jaws. in any event, however, the reverse stop means is very rugged and capable of withstanding heavy shock, say when the jaws are opened at high speed, and the mass of the outer ring 1 l is great.

In the use of the tong apparatus thus far described, the motor M is operated, in either direction, to rotate the pipe gripping means G at relatively high speed. To effect initial engagement of the jaws J with a pipe, the brake means B must be applied, to hold the inner, jaw carrying ring 10 against rotation with the outer ring 11 until the gripping of the pipe by the jaws'is sufficient to rotate the pipe, at which time self energization of the cam roller system works to assist in the gripping action. After the pipe is gripped, high braking effort is not desirable since the brake must be overcome by the tong motor M. Thus, the brake means B is preferably pressured to an extent determined by torque transmitted through the gripping means to the pipe. in addition, the lock means L should be released automatically when thespinning motor M is operated, and the lock means L should be engaged with the spinning motor locking gear 78 when the spinning motor is not operating to lock the spinning motor shaft, and more particularly, to lock the chain sprockets 76, when either of the actuator cylinder means MU or B0 is being operated.

The following is a description of the illustrative tong control system of FIG. 1 1, whereby the tong is operated as above described.

In order to operate the system, to make up and break out joints of pipe, a conduit 200 is connected to a suitable pressure source for supplying hydraulic pressure fluid from the source to a main motor control valve MV which has a neutral-position and selective positions for controlling fluid flow to the motor M in either direction, whereby the drive sprocket 78 for the chain means 12 will be driven in a selected direction to drive the gripping means G correspondinglyThus, when the main motor control valve MV is shifted to the right, as seen in FIG. 11, pressure fluid is supplied to conduit 300 M to drive the motor M in a make up direction,

and when the valve MV is shifted to the left, pressure.

fluid is supplied via a conduit 3008 to drive the motor M in a break out direction, in which case the motor is subjected to full source pressure from conduit 300. In the make up condition of the system, however, the maximum pressure supplied to the motor M via conduit 300M and therefore, the maximum motor torque output, or stall torque, is controlled by a motor torque limiting relief valve 300R connected to the make up conduit 300M by a conduit 301. The maximum pressure in the conduit 301 is adjustable by a variable regulator valve 301R which holds the relief valve 300R closed until the pressure acting on the regulator valve 301R relieves the bias pressure from the relief valve 3R.

Operating fluid pressure from conduit 300 is supplied via a conduit 300 to provide pilot pressure to a sequence valve 2038 which is normally closed to shut off the supply of fluid pressure from a supply conduit 303 to a pilot pressure conduit 304 which leads from the dequence valve 3028 to a pilot operated valve 304L which control the flow of pressure fluid fron the source conduit 303 via a conduit 305 to one or the other of the conduits 3001, and 306U by which the lock means L,

previously described, are operated to lock the motor M or release the lock. The sequence valve 3028 is controllable or adjustable by means of a variable regulator 302R which determines at what pressure in conduit 302, and hence, conduit 300, the sequence valve will open to supply pilot pressure to the lock control valve 304L to shift the latter from the normal position as shown to the alternate position to automatically pressurize the lock actuating cylinder 84 and engage the lock gear 78 with the lock dog 80. Thus, when the motor M stalls when spinning up pipe joints and greater torque is needed to further turn the pipe, the sequence valve 302$, responsive to increased pressure in the motor supply conduit will be operated to allow pressure to shift the lock control valve 304L to admit pressure to the lock cylinder 84 via conduit 306L to lock or anchor the chain 12 at the motor M, so that the make up actuator cylinder MU may be operated to finally make up the pipe joint. On the other hand, if a joint is to be broken out, the main motor valve MV will be operated to 'drive the motor in the break out direction and the .motor may stall, without initially breaking out the pipe joint, in which case, the sequence valve 3028 will also be operated to admit pressure to the lock valve conduit 304 to shift the pilot operated lock valve 304L to the lock engaging position, in which fluid flows to the cylinder 84 via conduit 3061,, and then the break out cylinder BO may be actuated to break out the joint.

The make up and break out actuators MU and B0, respectively, are controlled by a selector valve 3078 to which fluid is supplied via a conduit 308 from the source conduit 303.

In the position shown, the selector valve 307S directs pressure fluid from the conduit to the break out cylinder conduit 309B to cause extension of the rod 135, whereby the pipe gripping means G will be moved counter clockwise, as fluid returns to the tank from the make up actuator cylinder MU via the conduit 309M. In the alternate position, of course, the pressure applied; in the reverse direction will extend actuator rod 105, and fluid will be discharged back through conduit 3098. Since it is desired that the usual joints be made up to a prescribed torque limit, adjustable torque limiting valve means are provided in the pressure conduit leading to the make up actuator cylinder MU. Thus, a normally open valve 308R is interposed between the source of pressure and the actuator cylinder MU and is controlled by an adjustable, pressure responsive relief valve 309R which allows the valve 308R to close, when pressure in line 309M exceeds a selected level. On the other hand to allow full torque application to the pipe when breaking out joints, the conduit 3098 is exposed to the full pressure of source conduit 303.

The system includes brake control means, as previously indicated, for the brake means B. This control means functions to admit high pressure to the respective piston chambers 157 and 159 to force the pistons 160 toward the brake disc 150 or to reduce the pressure applied to the brake chambers 157, 159, depending upon whether more or less radial loading of the jaws J into gripping engagement with the pipe is necessary to prevent slipping of the gripping dies during engagement with the pipe and during spinning or make up or break out of the joint, as the case may be.

More particularly, fluid pressure is supplied to the brake chambers 157, 159 via a conduit 310 leading from the source conduit 303 under the control of a normally open reducing valve 310R which is regulated by an adjustable high pressure relief valve 31 IR or an adjustable low pressure relief valve 312R, depending upon the pressure of fluid in the supply conduit 300 for the motor M. Thus, a pilot pressure conduit 313 leads from the motor conduit 300 to an adjustable, normally closed relief valve 314R in a conduit 314 leading between the high pressure relief valve 311R and the low pressure relief valve 312R. When the relief valve 314R is closed, as shown, fluid is supplied through the normally open valve 310R at full source pressure from conduit 303 to apply a high braking force, limited only by the adjustment of the relief valve 31 IR, even though the motor M is inactive. When the motor control valve MV is opened to operate the tong gripping means, the

pressure in motor source conduit 300 will increase as the gripping means encounters resistance upon closure of the jaws on the pipe. Since the greater the encountered resistance, the greater the force applied by the cam ring 11 on the jaws J to grip the pipe, the pressure in the brake chambers is preferably reduced so that high brake force need not be overcome. The pressure in conduit 313, as it increases, will open the normally closed valve 314R, when 'the pressure equals the setting of the valve 314R, so that the reducing valve 310R tends to close, reducing the applied brake pressure in chambers 159. Thus, the brake control system is effective to maintain a high brake force to assure that the pipe gripping means securely grips the pipe without slipping thereabout, but when the high braking force is not needed, the pressure is relieved. This characteristic assures longer life of the pipe gripping dies 37'and minimizes damage to the pipe due to skidding of the dies around the pipe.

Additionally, the control system includes means for selectively operating the reverse stop actuator cylinders 180, only one of which is shown in FIG. 11, for simplicity. The source conduit 303, in the illustrated system, leads to a conduit 315 which is connected to a suitable selector valve 3158. In the position shown, the valve 3158 directs pressure fluid to the actuator via a conduit 315M to retract the actuator rod, and thereby position the reverse stop ring 178 in the make up position, as seen in FIGS. 5, 6, 7 and 9, and in the alternate position of the valve 315$, pressure fluid will be supplied via a conduit 315B to shift the actuator rod to an extended position and move the reverse stop actuator ring 178 in its alternate or break out position of FIGS. 8 and 10.

While the main control valve MV for the motor M, the make up and break out actuator selector valve 3078, and the reverse stop actuator selector valve 3158 have been herein shown, simply, as manually operated valves, it will be understood that the tong may be operated at a control consol having suitable means, electrical, pneumatic, or hydraulic for remotely operating the system or for integrating the system in an automatic well drilling rig.

From time-to-time, during the use, testing or construction of the tong, it may be necessary or desirable to drive the outer ring in either direction for closing the jaws, or the jaws may be inadvertently closed while no pipe is in the gripping means G. Under such circumstances, the reverse stop means also acts, since it includes opposing sets of lugs, to limit relative rotation of the inner and outer rings in a jaw opening direction, since the lugs 170a will engage either the lugs 174a or 1740, depending upon whether the tong is operating in a make up or break out direction and will limit movement of the cam surfaces 42M or 42B, respectively, relative to the rollers 40 more than 60, so that the inner and outer rings cannot be shifted out of phase with respect to the reverse stop means RS.

From the foregoing, it is believed that no further description of the mode of operation of the present tong is necessary, and that it is now apparent that the invention provides a novel, rugged and versatile power pipe tong.

lclaim:

1. In power tong apparatus for making up and breaking out threaded joints having relatively rotatable joint parts, a body having an opening for one of said joint parts, joint part gripping means rotatably carried by said body and extending about said opening, said gripping means including a jaw carrying member and a jaw actuating member mounted one on the other for relative rotation, means for driving said gripping means rotatively, said jaw carrying member having a plurality of gripping jaws movable between retracted positions and gripping positions in said opening for gripping engagement with a joint part upon relative rotation of said members in either direction, means on said jaw actuating member and on said jaws for actuating said jaws to said gripping positions in response to relative rotation of said members in either direction, aid jaws being movable to said retracted positions upon reverse relative rotation between said members and reverse stop means for limiting said reverse relative rotation between said members in either opposite direction whereby said members will rotate together when said jaws are moved to the retracted positions, the improvement wherein said reverse stop means includes a first stop element carried by one of said members and having stop lugs alternately spaced axially and angularly, a second stop element carried by the other of said members and having a cooperative lug movable when said jaws are in said retracted positions axially in the angular space between the lugs of said first stop element between alternate axial positions engageable with the lugs of said first stop element to limit reverse relative rotation between said members in either direction to locations at which said jaws are in said retracted positions while allowing relative rotation of said members in the other direction to allow said jaws to be actuated to said gripping positions, and means for relatively axially actuating said stop elements to alternately position said lug on said second stop element.

2. In power tong apparatus as defined in claim 1, said lugs on said firs and second stop elements being angularly extended a distance equal to the extent of relative rotation of said members necessary to fully move said jaws to said gripping positions, whereby said lugs on said first and second stops are also engageable to limit relative rotation of said members beyond the point at which said jaws are fully actuated towards said gripping positions.

3. In power tong apparatus as defined in claim 1, said lugs on said-first and second stops being in angularly spaced sets, and said lugs on said first and second stop elements being angularly extended a distance equal to the extent of relative rotation of said members necessary to fully move said jaws to said gripping positions, whereby said lugs on said first and second stops are also engageable to limit relative rotation of said members beyond the point at which said jaws are fully actuated towards said gripping positions.

4. In power tong apparatus as defined in claim 1, said means for axially actuating said stop elements between said alternate positions including an actuator member shiftable relative to one of said stop elements, and cam means on said stop elements.

5. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stoprings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings.

6. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuat ing said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, and means for shifting said latter stop ring axially upon rotation of said actuator ring relative to said latter stop ring.

7. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, means for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position, and means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction to said normal position.

8. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner.

5 ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, cam means between said actuator ring and said latter stop ring for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position, and means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction to said normal position.

9. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, means for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position and spring means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction to said normal position.

10. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements comprising stop rings carried by said inner and outer rings, one of said inner and outer rings and one of said stop rings having axially extended splines connecting the same for rotation and enabling axial movement of said latter stop ring relative to the other stop ring.

ll. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, one of said stop elements comprising a stop ring carried by said inner ring, the other of said stop elements comprising a stop ring carried by said outer ring, and said means for relatively axially actuating said stop elements includes actuator means interposed between said body and one of said stop rings.

12. In a power tong as defined in claim 1, said jaw carrying member comprising an'inner ring extending about said opening, said jaw actuating member comprising an outer ring extendingabout said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, one of said stop elements comprising a stop ring carried by said inner ring, the other of said stop ele- Ebi1$ii'i%3fi%5l iiiify iiitiitiiigiifi 235i elements includes an actuator ring interposed between said body and one of said stop rings, bearings between said actuator ring and the latter stop ring, cam means for moving said actuator ring axially in one direction from a normal position upon angular movement of said actuator ring in one direction from a normal position, shifting means for shifting said actuator ring angularly in said one direction and returning said actuator ring to said normal position, and means for returning said latter stop ring to its normal position upon return of said actuator ring to its normal position.

13. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam'and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, said first stop element comprising a stop ring fixedly carried by said outer ring, said second stop element comprising a stop ring axially shiftably carried by said inner ring in concentric relation to the stop ring carried by said outer ring, said lugs being on the confronting sides of said stop rings.

14. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, said first stop element comprising a stop ring fixedly carried by said outer ring, said second stop'element comprising a stop ring axially shiftably carried by said inner ring in concentric relation to the stop ring carried by said outer ring, said lugs being on the confronting sides of said stop rings and consisting of sets of lugs on the respective stop rings spaced about said stop rings, the angular extent of each set of lugs determining the maximum relative angular movement of said inner and outer rings in directions to move said jaws to said gripping positions.

15. In power tong apparatus as defined in claim 1, brake means for normally holding one of said members against rotation with the other of said members during movement of said jaws between said retracted and gripping positions. 

1. In power tong apparatus for making up and breaking out threaded joints having relatively rotatable joint parts, a body having an opening for one of said joint parts, joint part gripping means rotatably carried by said body and extending about said opening, said gripping means including a jaw carrying member and a jaw actuating member mounted one on the other for relative rotation, means for driving said gripping means rotatively, said jaw carrying member having a plurality of gripping jaws movable between retracted positions and gripping positions in said opening for gripping engagement with a joint part upon relative rotation of said members in either direction, means on said jaw actuating member and on said jaws for actuating said jaws to said gripping positions in response to relative rotation of said members in either direction, aid jaws being movable to said retracted positions upon reverse relative rotation between said members and reverse stop means for limiting said reverse relative rotation between said members in either opposite direction whereby said members will rotate together when said jaws are moved to the retracted positions, the improvement wherein said reverse stop means includes a first stop element carried by one of said members and having stop lugs alternately spaced axially and angularly, a second stop element carried by the other of said members and having a cooperative lug movable when said jaws are in said retracted positions axially in the angular space between the lugs of said firsT stop element between alternate axial positions engageable with the lugs of said first stop element to limit reverse relative rotation between said members in either direction to locations at which said jaws are in said retracted positions while allowing relative rotation of said members in the other direction to allow said jaws to be actuated to said gripping positions, and means for relatively axially actuating said stop elements to alternately position said lug on said second stop element.
 2. In power tong apparatus as defined in claim 1, said lugs on said firs and second stop elements being angularly extended a distance equal to the extent of relative rotation of said members necessary to fully move said jaws to said gripping positions, whereby said lugs on said first and second stops are also engageable to limit relative rotation of said members beyond the point at which said jaws are fully actuated towards said gripping positions.
 3. In power tong apparatus as defined in claim 1, said lugs on said first and second stops being in angularly spaced sets, and said lugs on said first and second stop elements being angularly extended a distance equal to the extent of relative rotation of said members necessary to fully move said jaws to said gripping positions, whereby said lugs on said first and second stops are also engageable to limit relative rotation of said members beyond the point at which said jaws are fully actuated towards said gripping positions.
 4. In power tong apparatus as defined in claim 1, said means for axially actuating said stop elements between said alternate positions including an actuator member shiftable relative to one of said stop elements, and cam means on said stop elements.
 5. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings.
 6. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, and means for shifting said latter stop ring axially upon rotation of said actuator ring relative to said latter stop ring.
 7. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, means for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position, and means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction To said normal position.
 8. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, cam means between said actuator ring and said latter stop ring for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position, and means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction to said normal position.
 9. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements respectively comprising stop rings carried by said inner and outer rings, one of said stop rings being axially shiftable with respect to one of the inner and outer rings, and the other of said stop rings being fixed with respect to the other of said inner and outer rings, said means for relatively axially actuating said stop elements between said alternate positions including an actuator ring rotatably supported relative to said axially shiftable stop ring, means for shifting said latter stop ring axially in one direction upon rotation of said actuator ring in one direction from a normal position and spring means for shifting said latter stop ring axially in the other direction upon rotation of said actuator ring in the other direction to said normal position.
 10. In power tong apparatus as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said stop elements comprising stop rings carried by said inner and outer rings, one of said inner and outer rings and one of said stop rings having axially extended splines connecting the same for rotation and enabling axial movement of said latter stop ring relative to the other stop ring.
 11. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, one of said stop elements comprising a stop ring carried by said inner ring, the other of said stop elements comprising a stop ring carried by said outer ring, and said means for relatively axially actuating said stop elements includes actuator means interposed between said body and one of said stop rings.
 12. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, one of said stop elements comprising a stop ring carried by said inner ring, the other of said stop elements comprising a stop ring carried by said outer ring, and said means for relatively axially actuating said stop elements includes an actuator ring interposed between said body and one of said stop rings, bearings between said actuator ring and the latter stop ring, Cam means for moving said actuator ring axially in one direction from a normal position upon angular movement of said actuator ring in one direction from a normal position, shifting means for shifting said actuator ring angularly in said one direction and returning said actuator ring to said normal position, and means for returning said latter stop ring to its normal position upon return of said actuator ring to its normal position.
 13. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, said first stop element comprising a stop ring fixedly carried by said outer ring, said second stop element comprising a stop ring axially shiftably carried by said inner ring in concentric relation to the stop ring carried by said outer ring, said lugs being on the confronting sides of said stop rings.
 14. In a power tong as defined in claim 1, said jaw carrying member comprising an inner ring extending about said opening, said jaw actuating member comprising an outer ring extending about said inner ring, said outer ring and said jaws having cam and roller means for actuating said jaws to said gripping positions upon rotation of said outer ring relative to said inner ring, said first stop element comprising a stop ring fixedly carried by said outer ring, said second stop element comprising a stop ring axially shiftably carried by said inner ring in concentric relation to the stop ring carried by said outer ring, said lugs being on the confronting sides of said stop rings and consisting of sets of lugs on the respective stop rings spaced about said stop rings, the angular extent of each set of lugs determining the maximum relative angular movement of said inner and outer rings in directions to move said jaws to said gripping positions.
 15. In power tong apparatus as defined in claim 1, brake means for normally holding one of said members against rotation with the other of said members during movement of said jaws between said retracted and gripping positions. 